Centerforce University #1 – Get Schooled on How a Clutch Works

Welcome to Centerforce University, where we will bring you all the clutch knowledge your gear-filled head can hold. In this, the first of five video installments in the series, the experts at Centerforce Performance Clutches give us a quick rundown of exactly how a clutch operates.

The flywheel bolts to a flange on the crank shaft, and will always spin at the same speed as the engine.

A clutch can be one of those mysterious parts where you might know what function it performs, but might not know exactly how it works. We asked Will Baty of Centerforce Clutches to give us a run-down of what is going on inside the bellhousing, and some of the factors that can affect a clutch’s performance.

The pressure plate bolts to the flywheel, and the clutch disc is sandwiched in between.

“A clutch creates the basic link between the engine and the transmission, and is the key to how the power of the engine is transferred to the transmission on its way to the wheels. The clutch’s main function is to temporarily disengage the engine from the transmission – allowing the engine to spin at a different rate – and allowing the driver to easily shift gears,” Baty explains.

The disc is where the magic really happens. The clutch disc is kind of like a big round brake pad, only instead of making things stop, it makes the transmission spin when the friction material grips the flywheel.

A clutch is actually several components working together to allow you to shift. Baty says, “There are four key components to a clutch system that allow it to do its job; the flywheel, the clutch disc, the pressure plate, and the throw-out bearing. All four work together as one unit. When you press the clutch pedal, the throw-out-bearing presses against the diaphragm fingers of the pressure plate, and the diaphragm raises, lifting the pressure plate ring away from the disc. The disc disengages, and you can shift.”

The throw out bearing pushes against the pressure plate's fingers when you press the clutch pedal. The fingers are "levers" that lift the pressure plate away from the clutch disc.

Clutches are able to operate thanks to friction and clamping forces. Friction keeps the clutch disc gripping the flywheel, and the clamp load of the pressure plate keeps the disc pressed to the flywheel, or allows it to release when you press the clutch. Baty tells us, “The amount of clamp load that the pressure plate generates, along with the type of friction material on the disc, are what determines the holding capacity of a clutch. There are many grades of friction material, or in the clutch world we call the ‘point of friction’, that can increase or decrease the clutch’s holding capacity. The higher the friction, the more holding capacity in the clutch, but typically the drivability will suffer. Another factor is the size and overall diameter of the clutch assembly; the larger the assembly, typically the more holding capacity, even at a lower pressure and point of friction.”

Stay tuned ye “scholars of shift” – in our next installment of Centerforce University, we will talk about the proper way to break-in a clutch.